I think it does a pretty good job at web app pen testing, but have found that Paros, w3af, and others find some vulnerabilities/items of interest that it doesn't. I also find that Wikto finds directories that Core doesn't.

An external network pen test is OK, but haven't found another tool better. Some of the OS fingerprinting is a little off and sometimes it cannot detect one at all.

Client-side is really good and have found a TON of corporate emails that I can use to leverage an attack.

One thing I find in an internal test is that Symantec Endpoint Protection goes berserk on the host that I am testing against. I guess that is a good thing though, but not for for me when I am testing.

I have used Core a lot to test vulnerabilties if I am attacking the network internally. It does a great job and is an asset to a pentester's tool box. However, if I am attacking from the "outside" I find its way too noisy. I hate getting shut down or alerting anyone of my attack early on, although sometimes I am amazed how asleep at the wheel some folks can be!

I still follow the concept of attacking a network the way a hacker would. Most black hats that I have been aware of dont have access to tools like Core and use more simple and stealth techniques. Thats been my experience.

Yes, it does a wonderful job pivoting through a compromised host and is very, very noisy. Another thing that they could do better is the reporting. If I were scanning for PCI compliance would want that reporting option, especially for the price you pay for it.

I feel you, Pizza. I was in the same boat years ago when I was looking for a vulnerability scanner. If they sniff the fact that you are hesitant or think you don't have the funding for it, they won't bother with you. At least that was my perception and that was back in '05.